1. Field of the Invention
The present invention relates to an improved process for dehydrochlorinating 1,1-bis(R-phenyl)-2,2,2-trichloroethanes.
2. Description of the Prior Art
The 1,1-bis(R-phenyl)-2,2,2-trichloroethanes are known to this art. For example, 1,1-bis(chlorophenyl)-2,2,2-trichloroethane (DDT) is an intermediate compound in the synthesis of 1,1-bis(chlorophenyl)-2,2,2-trichloroethanol, commonly known as dicofol, an acaricide applied to cotton crops and fruit trees.
DDT is dehydrochlorinated to 1,1-bis(chlorophenyl)-2,2-dichloroethylene (DDE) which is then chlorinated to prepare 1,1-bis(chlorophenyl)-1,2,2,2-tetrachloroethane (chloroDDT), which in turn is hydrolyzed to dicofol according to the reaction sequence: ##STR1##
Polish Patent PL-110,642 (Chemical Abstracts, Vol. 96: 122386 h (1982)) describes the dehydrochlorination of diphenyltrichloroethane (C.sub.6 H.sub.5).sub.2 CH--CCl.sub.3 to diphenyldichloroethylene (C.sub.6 H.sub.5).sub.2 C.dbd.CCl.sub.2, the process being carried out in benzene with sodium hydroxide and methylbis(polyoxyethylene)stearylammonium chloride.
Russian Patent SU-899,524 (Chemical Abstracts, Vol. 97: 55461 j (1982)) describes the dehydrochlorination of 1,1-bis(p-chlorophenyl)-2,2,2-trichloroethane (p--ClC.sub.6 H.sub.4).sub.2 CH--CCl.sub.3 with an alkali metal hydroxide, the process being carried out in ethanol or isopropanol.
And Polish Patent PL-112,229 (Chemical Abstracts, Vol. 96: 162301 h (1982) describes the dehydrochlorination of bis(para-hydroxyphenyl)trichloroethane (4--HOC.sub.6 H.sub.4).sub.2 CH--CCl.sub.3 in methanol in the presence of a basic, quaternary ammonium ion exchange resin.
The presence of a reaction solvent such as benzene, ethanol, isopropanol or methanol presents difficulties in the event that a chlorination is to be carried out downstream of the dehydrochlorination operation, because such a solvent can itself be chlorinated.
If the product obtained via the dehydrochlorination is to be isolated, the presence of solvent makes the separation more complex.